The research will determine the potential value of several bird species, which differ in life span, as models for the investigation of the biology of aging. Birds tend to be longer lived than mammals for any given body size, despite features of their biology (high metabolic rate, high body temperature) that should accelerate aging. Because they share a vertebrate genome with mammals, yet have a long independent history, study of their resistance to aging may reveal novel mechanisms that protect against aging, which can nevertheless be applied to prevention of aging damage in humans. Loss of ability for cell replication, caused by progressive shortening of terminal segments of chromosomal DNA called telomeres; and progressive oxidative damage to DNA and proteins are possible mechanisms of aging. This research will examine the mechanisms that permits exceptionally long-lived bird species to avoid telomere shortening as they age by measuring the expression and activity of telomerase, the enzyme complex that repairs telomeres. It will measure levels of oxidative damage in a variety of cell types in species that age at different rates and in individuals of different ages within each species, to determine whether long-lived species also have exceptional protection against oxidative damage. In mammal species including humans, telomerase is repressed in many somatic cell lines, perhaps as a mechanism for reducing the frequency of cancer. If long-lived birds continue to express telomerase in somatic cells throughout life, then how these species avoid telomerase's oncogenic effects will be of considerable interest. The results will indicate whether telomerase activity accounts for the protection of telomere length and life span in birds, provide models for searching for the mechanisms involved, and provide models for determining correlated traits that are necessary for long life.